/**
  * @param \OAuth2\Client\ClientInterface $client
  * @param string                         $grant_type
  *
  * @throws \OAuth2\Exception\BaseExceptionInterface
  */
 protected function checkGrantType(ClientInterface $client, $grant_type)
 {
     if (!$client->isAllowedGrantType($grant_type)) {
         throw $this->getExceptionManager()->getException(ExceptionManagerInterface::BAD_REQUEST, ExceptionManagerInterface::UNAUTHORIZED_CLIENT, 'The grant type "' . $grant_type . '" is unauthorized for this client_id');
     }
 }